This invention relates to a master cylinder for automotive vehicles and more particularly to a tandem master cylinder which comprises two independent fluid chambers fluidically connected to wheel cylinders.
In order to constitute two independent fluid chambers in the cylinder body it is necessary to provide a primary plunger to be actuated by the foot pedal and a secondary plunger operatively connected to the first plunger to define one of the two fluid chambers therebetween. In order to operatively connect the second plunger to the first plunger it is also necessary to provide a return spring interposed between the two plungers.
One type of such tandem master cylinders comprises an intermediate member slidably fitted to the first plunger and abutting the second plunger.
The intermediate member is provided primarily to define the distance between two plungers thereby permitting the setting load of the spring to be stronger than the setting load of the other return spring disposed in the other fluid chamber and normally urging the second plunger toward the first plunger. As a result, two fluid chambers may be pressurized simultaneously or one chamber may be pressurized in advance of the other chamber. In the event of the hydraulic failure of the one fluid chamber the second plunger will be mechanically actuated due to the sliding movement of the first plunger with respect to the intermediate member with the smallest loss of the pedal stroke.
Such an intermediate member comprises a retainer head which abuts on the second plunger to receive one end of the spring, thereby serving as a spring.
The conventional spring retainer, however, is of a diameter substantially equal to the diameter of the cylinder bore. Consequently, the inner wall of the bore is subjected to injury due to engagement with the retainer which is caused by vehicle vibration or the radial urging force of the spring on the retainer.